How to Plumb In 3rd SCV on John Deere 4520

If you own a John Deere 4520 compact utility tractor, you’ve probably run into situations where two hydraulic outlets just aren’t enough—maybe you’re running a grapple, snowblower, or log splitter that demands an extra control. That’s where learning how to plumb in 3rd SCV on John Deere 4520 becomes essential. This guide walks you through the entire process safely, clearly, and in compliance with best practices—so you can expand your tractor’s capabilities without compromising performance or safety.

Why Add a 3rd SCV to Your John Deere 4520?

The John Deere 4520 comes standard with two Selective Control Valves (SCVs), which are sufficient for basic implements like loaders or backhoes. But modern farming and landscaping often require three or more hydraulic functions simultaneously. A third SCV unlocks:

• Simultaneous operation of loader + grapple + rear implement
• Greater efficiency during complex tasks (e.g., snow removal with blade and chute control)
• Future-proofing for advanced attachments

According to a 2024 survey by TractorData.com, over 68% of compact tractor owners added auxiliary hydraulics within three years of purchase—primarily to support multi-function implements.

What Is an SCV? (And Why It Matters)

An SCV (Selective Control Valve) directs hydraulic fluid from your tractor’s pump to an implement. Each SCV controls one hydraulic function (e.g., lift, tilt, open/close). The John Deere 4520 uses an open-center hydraulic system with a gear-type pump rated at approximately 13.2 GPM (gallons per minute).

💡 Note: Adding a 3rd SCV doesn’t increase total flow—it splits existing capacity. Ensure your implement’s flow demand doesn’t exceed system limits.

For deeper technical context on hydraulic systems, see Hydraulic machinery on Wikipedia.

Tools & Parts You’ll Need

Before starting, gather these essentials:

⚠️ Warning: Never use generic hydraulic oil. The 4520 requires JD Hy-Gard LV (low-viscosity) to maintain valve responsiveness and prevent pump wear.

Step-by-Step: How to Plumb In 3rd SCV on John Deere 4520

Follow these precise steps to install your third SCV correctly and safely.

Step 1: Park Safely & Depressurize System

• Park on level ground, lower all implements.
• Turn off engine, remove key.
• Cycle all hydraulic levers (left/right, up/down) to release pressure.
• Wait 10 minutes before opening any lines.

Step 2: Locate SCV Mounting Position

• On the 4520, the factory 3rd SCV mounts between the existing two valves on the right side of the transmission housing.
• Remove the blanking plate (if present) using a 10mm socket.

Step 3: Install the SCV Valve Body

• Align the new valve with mounting holes.
• Torque bolts to 22 ft-lbs (per JD service manual).
• Ensure the spool lever moves freely before connecting hoses.

Step 4: Route Hydraulic Hoses

• Connect pressure line from main hydraulic manifold to SCV inlet (usually marked “P”).
• Run return line from SCV “T” port back to reservoir.
• Attach work ports (“A” and “B”) to rear hydraulic couplers using high-pressure hoses.
• Use hose clamps every 12 inches to prevent vibration damage.

🔧 Pro Tip: Label hoses with heat-shrink tags (“3RD-A”, “3RD-B”) for future troubleshooting.

Step 5: Refill & Bleed System

• Top off with JD Hy-Gard LV (capacity: ~10.5 quarts total).
• Start engine, idle at 1,200 RPM.
• Cycle the new SCV lever 10–15 times to purge air.
• Check for leaks at fittings—re-torque if needed.

Step 6: Test Under Load

• Attach a compatible implement (e.g., hydraulic top link or grapple).
• Operate slowly at first; verify smooth extension/retraction.
• Monitor hydraulic temperature—should stay under 180°F during normal use.

Common Mistakes to Avoid

Aftermarket vs. OEM SCV Kits: Which Is Better?

📊 Expert Insight: “OEM kits integrate seamlessly with the 4520’s hydraulic logic. For occasional users, aftermarket is fine—but commercial operators should invest in genuine JD parts.” — Mark Delaney, Certified Ag Technician (ASE Level 2)

FAQ Section

Q1: Can I add a 3rd SCV myself, or do I need a dealer?

A: Yes, many owners successfully install it themselves if they’re comfortable with hydraulic systems. However, if you’re unsure about routing lines or bleeding air, a certified John Deere technician is recommended—especially to maintain warranty coverage.

Q2: Will adding a 3rd SCV void my warranty?

A: Not if you use a genuine John Deere kit and follow installation guidelines. Modifications with non-OEM parts may affect coverage for related components.

Q3: How much does professional installation cost?

A: Labor typically runs $250–$450, depending on location and shop rates. DIY saves significant money but requires mechanical confidence.

Q4: Can I add a 4th SCV later?

A: Yes—the 4520’s hydraulic system supports up to four SCVs, but total flow must be managed carefully. Consider a flow divider or priority valve if running multiple high-demand implements.

Q5: Do I need electric solenoids for the 3rd SCV?

A: No. The standard 3rd SCV on the 4520 is mechanically operated via a lever in the cab. Electric SCVs are available but require additional wiring and switches.

Q6: Where can I buy the official John Deere 3rd SCV kit?

A: Order part #BW16167 through any authorized John Deere dealer or online via JohnDeere.com Parts. Verify compatibility with your serial number first.

Conclusion

Learning how to plumb in 3rd SCV on John Deere 4520 empowers you to tackle more complex jobs with greater efficiency—whether you’re managing a small farm, landscaping business, or rural property. With the right parts, careful installation, and attention to hydraulic best practices, this upgrade pays dividends in versatility and productivity.

✅ You’ve now got the knowledge to do it right—safely, legally, and effectively.

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